perf probe: Make synthesize_perf_probe_point() private to probe-event.c

Not used in any other place, so just make it static.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/ZM0pjfOe6R4X%2Fcql@kernel.org/


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>